In modern communication systems, signals may be transmitted from a source location to a destination location in analog or digital forms. As an example, the use of digital data communication may increase capacity of data transmission, flexibility of data manipulation, etc. Signals containing data, such as data derived from test, image, voice, video, etc., may be encoded into sequences of symbols or binary symbols, which are then transmitted from a transmitter to a receiver through one or more communication channels, such as via a cable or over-the-air.
In digital communication systems, data can be transmitted through one or more frequency bands within a finite frequency bandwidth. When multiple channels are used, these channels may overlap one another, and interferences may occur between the overlapped channels. One method to reduce or eliminate the interferences is to utilize orthogonal frequency division multiplexing (OFDM). In an OFDM system, a single channel may include multiple subcarriers having different but adjacent frequency bands. Although these subcarriers may overlap one another, they are orthogonal to one another, thereby reducing or eliminating the interferences caused by frequency overlap.
Examples of OFDM communication systems include systems complying with IEEE 802.16e or 802.16m standards. One version of such standards includes a proposal to IEEE C802.16m-08/1443 standard, titled “Proposed Text of DL Physical Layer Section for the IEEE 802.16m Amendment” (“Reference 1”). In a system consistent with Reference 1, permutation is utilized to increase the diversity of a channel coding block by changing the location of data subcarriers. It is preferable to evenly permute the contiguous data subcarriers in physical frequency to prevent a forward error correction (FEC) block from bursting errors. The forward error correction block is used to correct errors in the data stream as long as the number of the errors is under control. However, when there are too many errors in the FEC block, the FEC block can no longer be used to correct the errors. By applying permutation, the burst errors in frequency or time domain can be distributed to several FEC blocks so that each block can be used to correct errors. In the proposal to IEEE 802.16m standard, i.e., Reference 1, a large table of permutation sequences is relied upon to obtain the results of random distribution. However, this method may require a large number of additional memories or other storage devices for storing the large permutation sequence table, which may lead to increased hardware complexity and degraded system performance in certain applications.
Therefore, it may be desirable to have alternative communication systems and methods having alternative permutation schemes.